IN EXCEL WITH FORMULAS PLEASE!! In a sunny Southern town, there's an uptick in population during the summer months as seasonal residents from the Southern and Western States arrive. The local post office experiences varying staffing levels due to the low customer volume in the winter and high volume in the summer. The service rate of a postal clerk is $0\mathrm{.}6$ customers per minute. The post office counter has a maximum of four workstations. The objective is to maintain the maximum customer wait time in the system at $6$ minutes. On a specific Thursday afternoon, the expected arrival rate is $1\mathrm{.}6$ customers per minute, with three out of four workstations open.

A recent demographic study suggests that in the next three years, the arrival rate at the post office during the summer months may increase to $2\mathrm{.}5$ customers per minute. How many stations should be open to ensure that the maximum customer wait time in the system remains $6$ minutes or less?